1. Field of the Invention
This invention relates to a method of analyzing and optimizing design of integrated circuit (IC) designs. In particular, the present invention relates to a method of minimizing net delay by means of optimal insertion of internal library buffers into nodes of the net tree.
2. Description of the Related Art
An integrated circuit chip (hereafter referred to as an xe2x80x9cICxe2x80x9d or a xe2x80x9cchipxe2x80x9d) comprises cells and connections between the cells formed on a surface of a semiconductor substrate. The IC may include a large number of cells and require complex connections between the cells.
A cell is a group of one or more circuit elements such as transistors, capacitors, and other basic circuit elements grouped to perform a function. Each of the cells of an IC may have one or more pins, each of which, in turn, may be connected to one or more other pins of the IC by wires. The wires connecting the pins of the IC are also formed on the surface of the chip.
A net is a set of two or more pins which must be connected, thus connecting the logic circuits having the pins. Because a typical chip has thousands, tens of thousands, or hundreds of thousands of pins, that must be connected in various combinations, the chip also includes definitions of thousands, tens of thousands, or hundreds of thousands of nets, or sets of pins. The number of the nets for a chip is typically in the same order as the order of the number of cells on that chip. Commonly, a majority of the nets include only two pins to be connected; however, many nets comprise three or more pins.
The present invention involves a method for reducing delay of a net. The method includes constructing a time-space grid, said time-space grid corresponding to a net, passing a wave through the time-space grid, said wave having a wave value, and inserting a buffer at a point on said time-space grid where insertion of the buffer increases a wave value. The buffer can be a negative buffer or positive buffer. Generally, a second wave is passed through the time-space grid simultaneously with the first wave. Typically, the second wave and the first wave are inverted.